1. Field of the Invention
The present invention relates to a power board which is improved in the arrangement of its network receiving and transformer equipment.
2. Description of the Prior Art
In cities, vertical utilization of the land has been predominant and loftiness of buildings has been encouraged. A many-storied building has a distribution of power on load which is increased vertically and a very large load capacity, and because of many important public tenants or equipments accommodated in the building, it strongly requires reliability and safety of the power supply. Further, this type of building is located in a congested area of the city and therefore its installation area is desired to be as small as possible. Since in such a building or in a plant the load is concentrated to one location, a network receiving system is the most suitable because of its high reliability of supply of power.
In the network receiving system for receiving power from a power supply substation through 22 kV or 33 kV distribution lines of two to four circuits, only receiving breakers are disposed on the primary side of network transformers, fuses and protector breakers are provided on the secondary side in association with individual network transformers, the fuses and protector breakers are connected, on their load side, in parallel by network buses, and power is supplied to a variety of loads through distribution lines connected to the network buses. One may refer to U.S. Pat. No. 4,873,601 describing a spot network receiving system.
In the event that a short circuit occurs in the network system, for example, at the primary or secondary side of the network transformer, a faulty circuit can be disconnected and power can be supplied through a sound circuit to prevent the load from suffering from power failure, thus ensuring high reliability of supply of power. This meets the customer's needs and recently the demand for the network receiving system has been increased.
In the network receiving system, the network transformer, protector breaker and take-off breaker are housed in separate power boards and they are interconnected by distribution lines.
Accordingly, the installation area of the network receiving equipment is considerably increased only for the sake of installing the power boards and besides because of interconnections among the plurality of power boards, the wiring structure of distribution lines and network buses is complicated, making wiring work troublesome.
In addition, the separately installed network transformer, protector breaker and take-off breaker make it difficult to perform their maintenance/inspection. Conceivably, to cope with this problem, they may be stacked but in that case ease of push-in and pull-out working of the protector breaker and take-off breaker and ease of operation will be impaired. A power board disclosed in Japanese Utility Model Laid-open Publication Sho 56-100006 solves the problem of installation area but network buses disposed at a height raise a similar problem to the above.